Brief introduction of the hottest dry rolling gran

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Introduction to dry rolling granulation technology

dry rolling granulation technology is to process powdery chemical raw materials into granular products that meet the standard size and user requirements. The main technological processes include degassing, rolling, debris, whole grain, screening, etc. It has the characteristics of simple process, reasonable configuration, convenient operation and relatively low energy consumption. Stainless steel or titanium can be selected for the contact part of the unit with materials according to the properties of materials. Yufa rolling granulation technology has been applied in the granulation of TCCA and other products in the chlor alkali industry

1 Equipment Overview and function

the dry rolling granulation unit is mainly composed of the following single machines:

1 degassing tank: it is a device that temporarily stores powdered chemical raw materials and discharges part of the gas

2 agitator: its function is to evenly feed the raw materials sent by the degassing tank into the screw propeller after further mixing and degassing

3 screw propeller; It is a part that forcibly feeds material to the rolling mill. Its function is to pre compress the material before rolling and improve the density to meet the requirements of rolling. The screw propeller can use a governor to adjust the speed

4 sheet rolling machine: it applies a certain pressure on the raw materials and rolls the raw materials into sheets through the relative movement of two parallel rollers. The roll transmission adopts gear meshing transmission, and the center distance between the two rolls can be adjusted, with an adjustment range of 1 ~ 4 mm

5 fragment machine: it is a machine for crushing sheet materials. After crushing, the flaky materials become irregular granular and powdery mixture

6 pelletizer: during pelletizing, irregular granular materials are formed to make the particle size basically consistent

7 rotary vibrating screen: equipment for screening the particle powder mixture that has passed through the whole grain once. After screening, the particles that meet the requirements enter the finished product warehouse, and the rest return to the degassing tank

2 technical points in commissioning and operation

2.1 process flow and unit start and stop procedure

process flow is shown in Figure 1

when the unit is started, it shall be carried out in the reverse order of the process flow:

rotary vibrating screen - pelletizer - chipper - tablet rolling machine - propeller - agitator

when the unit is stopped, it shall be carried out in the sequence of the process flow:

agitator - propeller - tablet rolling machine - chipper - pelletizer - rotary vibrating screen

when the unit is stopped, the materials in the pelletizer, chipper, tablet rolling machine and rotary vibrating screen shall be cleaned to ensure the next smooth start

2.2 adjustment of thickness and strength of rolled sheet

thickness and strength of rolled sheet are the key to granulation quality. The center distance between two rolls should be kept at D+ 0.5 mm~do+6mm。 The initial center distance can be implemented by adjusting the shim thickness

it is recommended to do a good job in the normal protection of the oil pressure system, as shown in Figure 2

open the two stop valves of the hydraulic system, start the hand pump, when the system oil pressure meets the requirements, close the stop valve at the hand pump end, and the stop valve at the accumulator end is normally open. Only during maintenance, close this valve to store a certain amount of hydraulic oil. Under normal working conditions, the pressure drop caused by micro leakage can be compensated from the accumulator. After a certain period of operation, when the leakage is large and the accumulator is difficult to compensate, it is necessary to restart the hand pump to compensate the hydraulic oil to the system to maintain the stability of the system

after the above adjustment, the rolling mill can be started for trial operation. Adjust the rotating speed of the screw propeller during operation, and observe the thickness and strength of the rolled sheet until it meets the requirements

when the rolling mill works normally, the actual center distance of the roll is larger than the initial center distance, that is, under the condition of forced feeding, the upper roll floats upward

the above debugging should be repeated for many times until satisfactory results are achieved

2.3 several main factors affecting sheet thickness and strength

a speed of screw propeller; B. initial center distance of two rolls; C roll speed; D oil pressure; E characteristics of materials

generally, the sheet thickness increases with the increase of the rotating speed of the screw propeller, decreases with the increase of the pressure, decreases with the increase of the rotating speed of the roll, and increases with the increase of the stacking weight ratio of the material. The influence of the center distance between the two rolls is complex, which needs to be explored continuously in the commissioning

2.4 normal operation and maintenance of the unit

during normal operation of the unit, more than 50% of the volume of materials shall be maintained in the degassing tank in the first half of 2016

after the continuous operation of the unit, the temperature of screw propeller, rolling mill bearing, chipper, etc. may rise, but it is normal below 70 QC

the side seal of the tablet rolling machine and the screen plate of the pelletizer are vulnerable parts, which should be stopped and replaced in time when problems are found. Do not let hard foreign matters enter the running parts of the unit to avoid damaging the machine

the best data obtained in the unit commissioning and trial operation can be incorporated into the operating procedures. For a material, do not arbitrarily change the operating parameters in order to increase the output, so as not to affect the particle quality

this method cannot be used for granulation of some inflammable materials under rolling conditions

3 disadvantages and corresponding measures of dry rolling granulation

at present, the imbalance of oil resource reserves in various countries and the predatory mining granulation process in developed countries mostly adopt manual feeding. There are some leakage points at the connection of each single machine and the single machine itself in the process system, and there is dust in the operating environment

in order to improve the operating environment, the following measures should be taken:

1 reduce the leakage point of the machine itself, change the cloth bag of the soft joint into a sealed coating material, and change the feeding from open to opposite feeding, etc

2 corresponding air ducts are laid with 1 fan and cyclone separator for dust removal and ventilation near the feeding port

3 each unit is equipped with a bag of scientific and technological innovation positive wind-driven water-driven dust collector in China's high molecular material industry, and the interface is connected with the relevant parts of the unit

4 in the future, the development direction of dry rolling granulation is automatic conveying of materials and fully enclosed production. (end)

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